From the look of it you might have realized, but the 7300's don't run in SLI mode so there's no point. If you're going to need more graphics power, get the X1900 XT. But that extra GB of RAM would really help too.
Doubt the RAM prices will fall too much, sadly, for a variety of complex reasons about the future of FB-DIMM...but you will have time to save up for it.